Increasing the elastic modulus and hardness of low K films is one of the key
challenges towards integration of these materials into future integrated
circuits. Several approaches are explored for increasing the hardness of
carbon doped oxide (CDO) dielectrics. Several low K precursors and their
mixtures specifically chosen to enhance the hardness (H) and modulus (E) of
CDO films through chemically induced cross-linking. Composition and FTIR
measurements suggest the presence of C-C and C-Si cross-linking with
concurrent observation of improved film hardness and modulus at relatively
low deposition temperatures. Films deposited at 373°C using
diethoxy-methyl-oxiranyl have a hardness and modulus of 2.5 GPa and 18.1 GPa
respectively. Films deposited at 180°C using tetramethylcyclotetrasiloxane
(TMCTS) and 25% hardener have hardness and modulus of 1.5 GPa and 9.4 GPa,
respectively. These film properties are significantly higher than those
observed for TMCTS alone under similar deposition conditions. Based on these
results a low temperature process with 25% hardener and 75% TMCTS combined
with a porogen was used to produce a porous film with a k<2.5 and a
hardness of 0.72GPa.